An ideal composition for delivery of a topically-active compound to skin or hair delivers the topically-active compound such that it adheres to the skin or hair, while topically-inactive ingredients evaporate or are rinsed from the application site. Delivery of a water-insoluble topically-active compound is facilitated because the topically-active compound is not removed from the application site during the rinsing step. The difficulty with this type of composition resides in incorporating the water-insoluble topically-active compound into an aqueous composition. This difficulty is overcome by forming emulsions. Therefore, topically-active compounds, such as a hair conditioner, a hair dye, a skin care compound or a topical medicament, conventionally have been delivered from either oil-in-water emulsions or water-in-oil emulsions.
With respect to water-soluble and water-dispersible topically-active compounds (hereinafter collectively termed "water-soluble topically-active compounds"), it is easy to incorporate the topically-active compound into an aqueous rinse-off composition. However, a substantial amount, or all, of the water-soluble compound is rinsed from the treated skin or hair. The water-soluble compound therefore cannot perform its intended function and is wasted. Accordingly, rinse-off compositions often incorporate an excess of the water-soluble topically-active compound, such that a sufficient amount of the compound remains on the skin or hair after rinsing to perform its intended function. The need to overformulate is economically disadvantageous.
For example, water-soluble dyes are used in hair products because these dyes are semi-permanent, i.e., temporary dyes that do not dye the hair for extended time periods or through numerous shampooings. However, water-soluble hair dyes are difficult to apply because a substantial amount of applied dye is removed from the hair during the rinsing operation. Compositions incorporating water-soluble dyes also stain the hands of the applicator and various articles in the work area, such as sinks and countertops, both during product application and rinsing of the product from the hair.
Similarly, two-in-one products, like shampoo-conditioner compositions, have been difficult to formulate not only because of the water solubility of many quaternary ammonium compounds, but also because of the well-known incompatibility between an anionic surfactant and a quaternary ammonium compound. Formulators either have avoided this problem by sequentially contacting the hair first with an anionic surfactant, then a quaternary ammonium compound from different compositions, or have overcome this problem by using silicone conditioners in shampoo-conditioners. However, silicones and similar conditioners are water insoluble and an esthetically-unpleasant residue builds up on the hair after repeated applications. In addition, quaternary ammonium compounds impart hair conditioning properties different from a silicone, and therefore it is desirable to condition the hair with quaternary ammonium compounds in place of, or in conjunction with, a silicone.
Investigators therefore have searched for rinse-off, topically-effective compositions that overcome the above-described disadvantages, and that have consumer-acceptable stability and esthetics. A rinse-off, topically-effective composition however often is difficult to formulate because of the water solubility of the desired topically-active compound.
Many aqueous compositions are designed to be rinsed from the skin or hair after application. These include hair conditioners, hair shampoos, skin cleaners, facial scrubs, permanent wave lotions and temporary hair dyes. For many rinse-off products, it is desirable to leave one or more topically-active compounds on the skin or hair to perform an intended function. When the topically-active compound is water soluble, it is difficult, and often impossible, for a sufficient amount of the compound to remain on the skin or hair to be efficacious. Investigators therefore have directed their attention to compositions designed to be rinsed from the skin or hair after application and that are capable of depositing efficacious amounts of water-soluble, topically-active compounds to hair or skin.
One type of composition that has been investigated are multiple emulsions. Multiple emulsions are complex emulsions of emulsions formed by dispersing droplets in a continuous phase, wherein the droplets themselves contain smaller droplets of a liquid similar to the external continuous phase. One type of multiple emulsion is a water-in-oil-in-water emulsion (W.sub.1 -O-W.sub.2), wherein a primary water-in-oil (W.sub.1 /O) emulsion is dispersed in an external aqueous phase (W.sub.2). Multiple emulsions also are known as liquid membrane systems because, in the case of a W.sub.1 -O-W.sub.2 emulsion, an organic membrane, film or layer separates the inner water droplets from the external aqueous phase.
W.sub.1 -O-W.sub.2 multiple emulsion compositions have been used in the pharmaceutical industry as vaccine adjuvants and as sustained release and parental drug delivery systems. However, the low stability of W.sub.1 -O-W.sub.2 multiple emulsion compositions has limited their widespread use.
Multiple emulsion compositions also have been used in cosmetics and skin care products. W.sub.1 -O-W.sub.2 multiple emulsions however were difficult to prepare and were unstable at elevated temperatures. In addition, various active ingredients had a tendency to further destabilize the multiple emulsions, for example causing leakage between the external aqueous phase and internal aqueous phase.
W.sub.1 -O-W.sub.2 multiple emulsion compositions have been disclosed in numerous patents and publications. For example, M. C. Taelman et al., "Multiple Emulsions in Cosmetics", Publication RP112/94E, March, 1994, ICI Europe Limited, Everberg, Belgium, discloses multiple emulsions in general, including methods of manufacturing multiple emulsions. S. Matsumoto et al., J. Dispersion Science and Technology, 10 (1989), pp. 455-482, discloses the use of multiple emulsions in the food, drug and cosmetic industries.
Other publications which disclose multiple W.sub.1 -O-W.sub.2 emulsions are:
S. S. Davis et al., Encyclopedia of Emulsion Technology, Vol. 2; P. Becher, Ed.; Marcel Dekker, Inc., New York, N.Y. (1985), pp. 159-238; PA0 Y. Sela et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 83 (1994), pp. 143-150; PA0 K. Oza et al., J. Dispersion Science and Technology, 10(2) (1985), pp. 163-185; PA0 J. Zatz et al., J. Soc. Cosmet. Chem., 39 (May/June 1988), pp. 211-222; PA0 C. Fox, Cosmetics and Toiletries, 101 (November 1986), pp. 101-106 and 109-112; PA0 M. deLuca et al., Cosmetics and Toiletries, 105 (November 1990), pp. 65-66 and 69; PA0 T. Tadros, "Application of Multiple Emulsions in Cosmetics", ICI Surfactant publication RP56/92E (1992); and PA0 C. Prybilsky et al., Cosmetics and Toiletries, 106 (November 1991), pp. 97-100.
Various patents disclose multiple emulsion compositions used in cosmetic compositions. For example, WO 94/01073 discloses gelled multiple emulsion compositions for cosmetic use. Other patents include WO 94/02120; WO 93/00160; WO 92/18227; JP 58 183 611; U.S. Pat. No. 5,306,498; and U.S. Pat. No. 4,988,456.
U.S. Pat. Nos. 5,277,899 and 4,963,348, and WO 93/07848, disclose conditioners that have set retention properties. The disclosed compositions are oil-in-water emulsions (O/W), as opposed to the present W.sub.1 /O primary emulsions and the W.sub.1 -O-W.sub.2 multiple. emulsion compositions.
Although various patents and publications disclose W.sub.1 -O-W.sub.2 multiple emulsion compositions for cosmetic use, those compositions are designed as leave-on products, i.e., products that are applied to, and not subsequently rinsed from, the skin or hair, and that are allowed to remain in contact with the skin or hair. The present invention therefore is directed to W.sub.1 -O-W.sub.2 multiple emulsion compositions which are capable of depositing water-soluble, topically-active compounds onto hair or skin from rinse-off compositions, such as hair conditioners, hair shampoos, or skin cleaners.